We are just north of the Amazon Basin, riding a boat on the Ikabaru River. The passengers are people who buy gold and diamonds. They stop at each of the illegal mines that appear as craters on the river’s edge. They carry small weighing scales that seem very accurate, magnifying loupes, burners to melt the gold and separate the mercury, and some large spoons to collect it.

They are also carrying bags full of cash.

Jorge Silva / Reuters

An illegal mine is seen in the southern Venezuelan state of Bolivar, near the border with Brazil.

Jorge Silva / Reuters

A man performs maintenance while sitting on the top of an Antonov An-2 aircraft before it departs with supplies to the mines, in the town of Ikabaru in the south of Venezuela.

The appeal of working in illegal mining is enormous. Four grams of gold equal an average monthly wage in Venezuela. An ounce of the metal goes for over $1,700. The gold fever is understandable if you consider that an ounce used to sell for $250 ten years ago.

But in these mines, and the towns around them, life is expensive. A bottle of water costs around $12, and a 250-liter tank of gasoline, which would cost just $5 in the rest of the country, here goes for up to $1,200. Venezuela is known for having the cheapest gasoline in the world.

Those who can, work hard. They don’t know if they will be able to carry on. The government is threatening to clamp down on clandestine mining. Thousands of families and whole towns live off this activity, directly or indirectly.

Jorge Silva / Reuters

A garimpeiro digs with a pressure hose in Bolivar.

Jorge Silva / Reuters

Heavily armed guards hold their weapons outside a business licensed to buy rough diamonds and gold in Georgetown, the capital of Guyana.

In a city nearby, a diamond buyer adjusted the gun on his waist while he greeted a miner who brought some “rocks.” He passionately explained that diamonds are the perfect currency. “You can carry thousands of dollars in the pocket of your pants without setting off any metal detector. There are no borders for them.”

Back at the mine, Ramón walked exhausted at the end of his workday. His face, ravaged by the sun, was sprinkled with mud. When he smiled, a golden “R” became visible, inlaid in one of his front teeth. Read the full story.

Jorge Silva / Reuters

An miner named Ramon flashes a gold letter 'R' on his tooth as he smiles after working in a mine in Bolivar.

Editor's note: Images taken in November, 2012 and made available to NBC News today.